This application claims priority of International application number PCT/DE99/03074, filed Sep. 20, 1999, which in turn claims priority to German patent application number 198 44 293.9, filed Sep. 18, 1998.
The invention relates to a lighting device.
By contrast with incandescent lamps, discharge lamps have the advantage of a substantially higher light yield and/or economic efficiency. The operation of discharge lamps requires a ballast and a starting device, of which the starting device provides the starting voltage required for starting the gas discharge, whereas the ballast limits the lamp current of the discharge lamp during its operation after it has been started.
The starting voltage must overcome the resistance in the discharge lamp, and is proportional to the prevailing gas pressure. It can be up to 50 kV, but must be present only briefly as a high-voltage pulse.
After the discharge lamp has been started, resistance decreases inside the discharge lamp, and the lamp current, previously very low, can rise to impermissibly high values owing to the negative resistance characteristic of the ionized gas. A ballast with a positive current-voltage characteristic is therefore necessary to limit the current. Ballasts can be constructed as inductor ballasts or as electronic ballasts, it being impossible to achieve a robust design, a high operational reliability and ease of use with inductor ballasts. However, they require a relatively large lamp installation space, cannot compensate the lamp tolerances and changes in system voltage, and are relatively heavy.
Electronic ballasts compensate fluctuations in system voltage and in frequency over a certain range, but are less robust and likewise require installation space and appropriate cooling devices, and entail additional weight.
The operation of a discharge lamp by means of a ballast and starting device is general prior art, and is described in DE 43 01 184 C2, for example.
Normally, ballast and starting device are accommodated in the housing of the lighting device, that is to say in the vicinity of the discharge lamp, since in the case of a large length of lead from the ballast and starting device to the discharge lamp excessively large losses occur and/or an excessively large voltage drop occurs, and so reliable operation of the discharge lamp is not ensured. However, the lighting device becomes very large and cumbersome when the ballast and starting device are connected to the discharge lamp.
A further disadvantage of the known lighting devices consists in that a dedicated ballast and/or starting device is required for each discharge lamp, and this leads to substantial costs when a plurality of discharge lamps are used.
U.S. Pat. No. 5,691,603 discloses the connection of a plurality of lighting units to a central power supply, with a rectifier connected to a voltage source and having a downstream smoothing circuit to which an inverter bridge circuit is connected as a starting circuit for a plurality of lighting units. A socket of the central power supply is connected via fuses to an output transformer of the inverter bridge circuit and can be connected to a plug which produces an electric connection to the socket of a first lighting unit via a connecting line. This first lighting unit includes a ballast transformer and a series inductor and a fluorescent lamp.
Also provided is a through line which connects the socket-contact of the first lighting unit via an output socket-contact fitted on the first lighting unit to a further lighting unit which likewise includes a ballast transformer, a series inductor and a fluorescent lamp.
This document does not indicate how a compact structural unit can be created between the discharge lamp and an external starting device, on the one hand, and the discharge lamp and a ballast and basic starting device, on the other hand.
DE 33 23 930 A1 discloses a ballast and starting device for a gas discharge lamp fed from an AC circuit, which combines power-independent switching elements, specifically a rectifier bridge circuit, a current-limiting capacitor, a rectifier multiplier circuit and a bipolar, electromagnetic current impulse changeover switch in a starting section housing, and power-dependent switching elements, specifically series-connected capacitors with parallel-connected smoothing capacitors and a discharge resistor in a nominal power section housing can be interconnected electrically and mechanically via plug-in contacts, it being possible to connect the discharge lamp with an upstream smoothing inductor to DC voltage outputs of the starting section housing.
It is the object of the present invention to create a lighting device which can be used in a versatile fashion and even in the case of restricted available space, is of low weight and overall volume if required, ensures a compact, closed design, can be produced cost-effectively, and ensures stable operation which is insusceptible to interference.
The operation of the lighting device in various arrangements of a discharge lamp with a ballast and starting device widens the field of use of such lighting devices and also their ease of use, and permits cost-effective production and cost-effective operation of the lighting devices.
Since the discharge lamps are connected mechanically and electrically in a detachable fashion to the ballast and operating device, it is possible for different, and also a plurality of, discharge lamps to be operated simultaneously with one ballast and starting device.
A discharge lamp with small dimensions which can also be used at locations which are difficult to access is created by the mechanical and electrical coupling of the discharge lamp to an external starting device, which is connected via a connecting cable to the current-limiting circuit of a ballast and basic starting device in conjunction with bridging of the starting circuit of this device.
Since the discharge lamp is operated spatially separately from the ballast and basic starting device, the discharge lamp can be started independently of the relatively large and heavy ballast and thus has a low weight and can, in particular, advantageously be used in constricted space conditions. The transmission losses and voltage losses are minimized by the short spacing and the short line paths, associated therewith, between the discharge lamp and external starting device, thus ensuring reliable operation of the discharge lamp.
It is recommended in this case that when the discharge lamp is operated with an external starting device the adapter is used to produce a direct connection, avoiding the basic starting device, to the ballast by bridging the current-limiting circuit of the basic starting device. This can be done, for example, by an appropriate electric or electronic circuit arrangement, a switch or via a connect assignment of the adapter. In addition to low electric losses and to produce a closed structural unit between the external starting device and the discharge lamp, the external starting device can be fastened directly without further adapters on the discharge lamp, or on the housing of the discharge lamp.
In an advantageous development of the invention, the connection between the discharge lamp and housing of the ballast and basic starting device is implemented via an adapter, by means of which an interface is produced between the ballast and basic starting device and discharge lamp which is fixed and can be applied for a plurality of units. The adapter can be a separate component or integrated into one of the modules to be connected.
In one variant of the invention, a plurality of adapter connections are provided on the starting device so that a plurality of discharge lamps can be started with the aid of one starting device. Particularly in the case of electronic ballasts, it is possible for the lamp current of a plurality of discharge lamps to be controlled with the aid of a single ballast.
For reasons of easy assembly and of quick lamp changing, given that it is also possible to operate different discharge lamps on one external starting device, it is expedient for the external starting device to have an adapter connection of the ballast and basic starting device. It is possible in this way to operate the discharge lamp via an adapter connection both on the ballast and basic starting device and on the external starting device, without the need for structural changes or adapters.
It is favorable to be able to connect the connecting cable to the ballast at various points of the external starting device in the interest of the most variable use possible of the discharge lamp in the uncoupled mode. For this reason, the connecting cable has a plug which can be connected to a plurality of sockets of the external starting device.
An advantageous refinement of the solution according to the invention is characterized in that the sockets of the external starting device have different alignments or orientations. For example, one orientation is provided in the direction in which the lamp emits light, and one is provided at right angles to the direction in which the lamp emits light, in order to have as large a number as possible of options for combinations and arrangements in conjunction with the possible forms of plug, for example straight or right-angle plugs. Of course, other orientations relative to the direction of light emission or a main direction of expansion of the lamp housing are possible.
In accordance as well, it is advantageous for reasons of variability that the sockets and the adapter connections are compatible, so that, for example, a plurality of discharge lamps can be connected to a ballast by means of the external starting devices in different directions of light emission.
In one embodiment of the invention, the adapter connection or the sockets is constructed as a bayonet lock, the bayonet lock advantageously having a rotatable contact plate, in order not to damage the mechanical locking of the electric contacts.
The idea on which the invention is based is to be explained in more detail with the aid of exemplary embodiments illustrated in the drawing, in which: